This invention relates generally to transmission lines that carry electronic signals and more particularly to a system and method for planar transmission line transition.
Electrical signals such as microwave or millimeter-wave signals may be communicated across an electrical circuit using various types of planar transmission line structures. When more than one type of planar transmission line is used, transitions between the various structures are necessary. Conventional transition structures are susceptible to signal losses from both signal reflection and signal transmission. Conventional transmission structures also occupy significant amounts of scarce surface area in integrated circuit designs, which in turn limits efforts to miniaturize circuits.
According to one embodiment of the invention, a planar transmission line transition system includes a coplanar waveguide transmission line that includes a first electrical path and a second electrical path. The planar transmission line transition system also includes a transmission line stub electrically connected in series to the first electrical path of the coplanar waveguide transmission line, wherein a signal output at a first connection of the transmission line stub is phase delayed approximately 180 degrees with respect to a signal input at a second connection of the transmission line stub. The planar transmission line transition system further includes a transmission line electrically connected to the second electrical path of the coplanar waveguide transmission line and the first connection of the transmission line stub.
Some embodiments of the invention provide numerous technical advantages. Other embodiments may realize some, none, or all of these advantages. For example, according to one embodiment, the size of the transmission line stub is reduced by employing a slow-wave structure. Reducing the size of the transmission line stub significantly reduces the surface area required for the planar transmission line transition system, and may be useful in microwave or millimeter-wave electronics systems where miniaturization is desirable. In some embodiments, the planar transmission line transition system minimizes signal loss due to reflection or transmission.